1. Field of the Invention
The invention relates to a semiconductor mounting apparatus with a chip gripper which is moveable back and forth between a first location and a second location by means of a lever mechanism, in order to lift a chip from a chip carrier at the first location and to lay the chip on a substrate at the second location. Such an apparatus, described as a "pick and place" apparatus is used as a component of a mounting machine known as a "die bonder" in semiconductor mounting. It serves to mount the numerous similar chips of a wafer, which are located next to one another on a carrier, one after another on a substrate, for example, a metal lead frame. Coordinated with each pick and place movement, the wafer table on which the chip carrier is located makes available a next chip at said first location, and the substrate is also advanced in order to make available a new substrate location at the second location. For lifting up and subsequent laying down of the chips, the chip gripper can be raised and lowered in a known manner, either together with the whole apparatus or on its own relative to the apparatus. Extremely high demands are made on mounting apparatus of this type. For the further processing of the mounted chips (contacting of the integrated circuit in the wire bonder), the chips must be accurately positioned on the substrate, which requires a correspondingly accurate arrival at the second location by means of the chip gripper, and also necessitates the previous precise transporting to the first location for lifting up the chip. On the other hand, high speeds and short cycle times of the movement sequences are required, which cause correspondingly high accelerations and inertial forces to occur on the parts moved.
2. The Background Art
Up until now different lever mechanisms have been used to produce the alternating movements of the chip gripper, which sometimes include guide slots (for example, in the manner of the known maltese transmission arrangement). Such slots are disadvantageous for achieving precise movement because of the considerable shearing forces occurring with them, and have to be serviced accordingly. With another known mechanism, the chip gripper is seated at the end of a lever pivoting back and forth, that is to say it performs a curve-shaped movement corresponding to the swinging displacements of the lever, which must always be stopped in the end positions, wherein there is a strong tendency for vibration. With the known arrangements it is therefore difficult to satisfy the demands existing in practice with respect to accuracy as well as to speed.
The object of the invention is to overcome the existing disadvantages of the prior art with a semi-conductor mounting apparatus of the type described in the introduction. The pick and place mechanism must, above all, ensure accurate positioning of the chip gripper in both end positions, but along with this also make possible rapid back and forth movements, that is to say short cycle times.